M/F PhD position on colloidal nanomaterial assemblies for optical gain

Job Description

Thesis Subject

Summary of the PhD project:
Colloidal nanocrystals, or quantum dots, are semiconductor nanoparticles grown in solution using wet chemistry approaches. This PhD project aims at using colloidal nanocrystals as optical gain material for integrated lasing applications. The candidate will start by synthetizing state-of-the-art quantum dots with gain properties in the visible and participate to the construction of a new optical setup dedicated to advanced spectroscopy of those objects. Pump-probe transient absorption spectroscopy will be used to investigate QD optical gain metrics (bandwidth, lifetime, thresholds…) under optical excitation. The candidate will then explore more complex nanocrystal architecture, in particular targeting the development of as assemblies of different types of nanocrystals. This approach has two goals: obtaining new optical gain properties not accessible with single-component materials, such as ultrawide gain bandwidth or low-threshold lasing in highly coupled donor-emitter structures. The candidate will design and evaluate the potential of those metamaterials in the liquid state, and measure solid-state lasing performances. This project is funded by the ANR JCJC MetaQD.

Context:
Colloidal quantum dots (CQDs) are nanoparticles of semiconductor that, due to their size (2-20 nm), fall in the quantum confinement regime. As such, these materials exhibit optical properties that can be continuously adjusted over a wide range of wavelengths, from the infrared to the ultraviolet. CQDs are already used in next-generation displays (Samsung QLED), infrared sensors (ST Microelectronics, IMEC) and as bio-tagging materials. The next step for these materials is the democratization of their use as a source of laser light, that requires the nanoparticles to sustain very high excitation levels. The process of stimulated emission, responsible for emission of coherent laser light, is a collective process that requires nanocrystals to be packed together tightly, typically in solid state films. The solution processability of nanocrystals makes them a great candidate for on-chip integrated photonics, where integration of light sources remains complex due to the constraints of epitaxy. Very recently, the proof-of-concept for an electrical CQD device capable of emitting light in the optical gain regime (ie, able to reach the population inversion regime and of amplifying light) have been demonstrated. There is now a need to obtain more tools for the rational design of optical gain properties beyond the single material, especially to solve the challenges associated with high optical gain thresholds.

Objectives:
Synthetize state-of-the art nanomaterials for the visible range, build a transient absorption spectroscopy setup dedicated to optical gain measurements. Design new QD assemblies allowing for gain properties to emerge from the collective behavior or the interplay between materials. Bring those new properties to solid-state lasing devices under optical excitation.

Methods :
• Material synthesis
• Ultrafast spectroscopy
• Nanofabrication
• Time-resolved experiments
• Nanoscale assemblies
• Optical design
Expected results :
QD formulations allowing to unlock optical gain properties unobtainable with single material approaches, optimized QD lasers in the solid state.
Themes:
Colloidal chemistry, materials for optoelectronics, nanosciences, photonics, optics, ultrafast spectroscopy.

Scientific and financiary conditions:
Synthesis in chemistry laboratory, spectroscopy experiments in optics laboratory. Work with class IV lasers. Project funded by ANR JCJC MetaQD.

Publication objectives :
Publications in peer-reviewed journals, participation to conferences in the national and international scopes.

Your Work Environment

PMC is one of 22 laboratories located at the Ecole polytechnique research centre working on the frontier of knowledge on the major interdisciplinary scientific, technological and societal issues.
Within the Teaching and Research Department of Ecole polytechnique, PMC (Laboratoire de Physique de la Matière Condensée) is a mixed research unit (Ecole polytechnique/CNRS) whose work is organized around two fundamental topics that are the nanosciences and the physics of Irregularity.
We try to understand the solid, liquid or intermediate states (gel, pastes, foams…) of matter (structure, properties, phenomena of sets related to the interactions between the particles that compose it), the condensed matter physics is a science that is upstream of innumerable technological advances.

The PhD student will be part of the IP Paris Doctoral School. The student will be part of the solid-state chemistry group at PMC. The student will participate to national meetings (GDR, workshops…) in his 1st year, and to international conferences in his 2nd or 3rd year. The student will visit collaborating laboratories in France (INSP Sorbonne University, Soleil Synchrotron, MPQ University Paris-Cité…). Potential trips to visit collaborators in Los Alamos National Laboratory (USA) and in Korea.

Constraints and risks

The candidate will work with chemicals (chemical safety risk), ultrafast and high-power lasers (laser risks). He/she will be trained accordingly.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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